In order to increase sales of products in which a variety of establishments deal, the following technique has been known in recent years. By pre-recording in an information distribution device advertising information indicating an advertisement for products of an establishment, the information distribution device distributes the advertising information (notification information) via a network to portable terminals (mobile terminals) owned by an indefinite number of users at the same time (see Japanese Laid-open Patent Publication No. 2001-350941, for example). For example, such an information distribution device determines whether to distribute the advertising information or not in accordance with the current locations of users' portable terminals. Specifically, the information distribution device distributes the advertising information to portable terminals located within a certain range of the establishment dealing in the advertised products (e.g., within a 10-km radius of the establishment). That is, the area within the certain range of the establishment is set as the distribution area.
However, when the distribution area covers a wide range, the advertising information is also distributed to portable terminals owned by users who absolutely have nothing to do with the establishment, for example, those who are far away from the establishment. In other words, when the distribution area covers a wide range, advertising information unnecessary to a large number of users is distributed to their portable terminals. As a result, the advertising expenses (communications expenses) borne by the proprietor of the establishment increase. Also, it is very bothersome for the portable terminal users because unnecessary advertising information is distributed to them.
In order to solve such a problem, there has been proposed an information distribution device that confines the distribution area and distributes advertising information only to users' portable terminals located in the vicinity of the establishment (e.g., within a 500-m radius of the establishment) (see Japanese Laid-open Patent Publication No. 2005-345325, for example). However, contrary to the problem described above, when the distribution area is confined, the advertising information may not be distributed to users who wish to receive the advertising information with their portable terminals. This can result in a reduction of the advertising expenses but the sales of products (profit of the establishment) do not rise more than a certain amount.
For this reason, there has been proposed an information distribution device that dynamically changes the distribution area in accordance with whether or not portable terminal users have read advertising information distributed to them (see Japanese Laid-open Patent Publication No. 2006-60454, for example). Specifically, the information distribution device expands the distribution area when there are a large number of users who have read the advertising information and narrows the distribution area when there are only a small number of users who have read the advertising information. Consequently, it is possible to reduce the advertising expenses while ensuring the profit of the establishment to be more than a certain amount as compared with the forms with a fixed distribution area.
However, since the conventional information distribution devices described above each set the area within a certain range of an establishment as the distribution area, problems such as the following occur even if the distribution area is changed dynamically as in the described-above case.
As an example, it is assumed that an establishment is located on a main line running in an east-west direction. In this case, since portable terminal users on the main line in the east-west direction are accessible to the main line, they are likely to visit the establishment if advertising information regarding the establishment is distributed to their portable terminals. In contrast, users located in the north-south direction with respect to the main line are not accessible to the main line. Thus, they are less likely to visit the establishment even if the advertising information is distributed to their portable terminals.
For this reason, when the advertising information is distributed to portable terminals located within a certain range of the establishment in a uniform manner as in the conventional information distribution devices described above, the advertising information may be beneficial to the users located on the main line in the east-west direction but be useless to those located in the north-south direction with respect to the main line. In other words, since the area within a certain range of the establishment is set as the distribution area, even if the distribution area is changed dynamically, advertising information unnecessary to a large number of users is distributed to their portable terminals.